We told him that the fiction we enjoyed reading the most was fantastic in nature, but this answer didn't appease him as we all admittedly read across many genres
It wasn't until I told him why fantasy was, at the time, easier for me to write that he seemed enlightened. At sixteen, I had (perhaps) half-a-clue as to why people behaved the way they did. Oh, I was engaged in social groups, but half the time I wasn't able to predict how I would react in a situation let alone how other people would. I didn't understand fully what motivated people or how they expressed those emotions, but I cared about getting it right in my fiction. And I just wasn't able to. But when I wrote second-world fantasy, I could make up some cultural/magical reason for my character's behavior. Having a malleable world let me fill plot holes with fantasy putty.
I've since come to what I hope is a more sophisticated understanding of plotting and world building than I had at sixteen, but the putty or plaster-and-paint-over of fantasy writing was necessary to keeping me writing for years as I came to understand better how humans worked and how the adult world worked. I suppose I could have solved the same problem by setting all my stories in a high school, but that approach brought its own risks (and still does): anytime you write about a setting that too closely resembles your day-to-day life, people assume that you're writing about yourself / people you know. Getting caught in such a situation in high school can be the end of the world. Post-high school it's still pretty damn annoying.
Recently, a discussion came up about which genre was more "freeing" for a writer, science fiction or fantasy. As in, in which of these speculative sub-sets does a writer have more freedom to "just make stuff up." The initial question was posed with a predisposition toward sci-fi as freer, which given my experience, struck me as a goose of strange feathers: I would have never been able to use fantasy as putty if it hadn't been freeing.
As as teen, I also tried writing sci-fi, but like urban fantasy, sci-fi rests on the presupposition that our current society has developed into the story's society. So I'd still have to understand people to build the story. Unless the story was full of aliens, then rock on. But for fantasy set in a secondary world, even if it was pseudo-medieval, it was never actually "earth," so I could wend as I wanted.
Classic (i.e. mid-century) science fiction was open to a lot more possibilities. Recent trends in sci-fi suggest that it should be bound by known physics ... which has led us to lots of post-apocalyptic Earth-based stories since so many scientists believe that faster-than-light travel was impossible (although that opinion might be changing), so we couldn't have space operas or alien encounters (the odds of humanoid life developing independently on another planet are ... minuscule), or space federations or Death Stars, or ray guns, or living ships ... in short, it got serious about its science, which curtailed the freedom of writing sci-fi while sucking the fun out of reading it.
Similarly, there's been a movement in second-world fantasy fiction to make the worlds more rule-based and harshly criticize any novels that don't make rigid physics-like rules for their worlds. Destroying the freedom of bending fantasy into any shape you want and -- to make a personal appraisal -- giving us fantasy novels like Game of Thrones which has a pseudo-medieval setting but very, very few traces of magic and speculative wonder in it. And what magic there is, is disapprovingly scrutinized.
Anecdote: I once heard that a reader, upon meeting George RR Martin, questioned him on why he had a giant wall of ice in his novel as it was physically impossible. GRRM (not pleased by the question) responded, "it's magic."Personally, I think it's a question GRRM set himself up for by having a world that was so rule based, so seemingly real that the presence of magic sat with the reader as ... odd.
But the notion that science fiction should be bound by physics and fantasy should be bound by a rule system as rigorous and rigid as physics is only one school of thought.
There's another school of thought out there that writers should reclaim the fun and freedom of science fiction and fantasy. That says let magic be magical, not so rigorously studied and understood that there could be a Wikipedia page on it. See N. K. Jemisin's beautiful piece where she asks "Why Does Magic Have to Make Sense? A piece she opens with the Arthur C. Clarke quote "Any sufficiently advanced technology is indistinguishable from magic." There's a revival of this fun and freeing fiction going on. I feel it's more noticeable in science fiction as editors and writers take a stand against the dark depressing overtones and produce works like Far Orbit: Speculative Space Adventures, which is coming out in spring 2014.
I say hurrah! to putting the fun and freedom, the mystery and magic, the awe and wonder back into science fiction and fantasy. A novel should, of course, always make sense, but I say that having a malleable world is a beautiful thing, and so long as a writer is willing to sand and paint after they've plastered some strange magic into their world, then bravo!, it need not be one continuous, unblemished piece of drywall. Why take some beautiful, wondrous, unexplained but unblemished creation like an energy field created by all living things that surrounds us, penetrates us, and binds the galaxy together ... then go and kill the wonder and restrict its freedom by quantifying it into a threshold number of midichlorians?
Top photo credit: "Students' notice board, 1973," LSE Library via Flickr.